Abstract : Trial Q21O was undertaken in November 1993 on CFAV QUEST to measure hull pressure loads and structural response during various operational conditions in moderate seas. This memorandum describes results of measurements and predictions for ship motions and for the pressure loads; results for the strain measurements and predictions will be discussed in a later report. Pressure spectra derived from the measurements are compared to predictions from PRECAL, a three-dimensional linear ship motion and load prediction code. The measured and predicted pressure spectra show reasonable agreement, indicating the strong potential of using PRECAL to predict fatigue load histories for ship hull structures. This report is presented in two volumes with Volume I containing the main body and Volume II containing the Appendices. Volume I will be given full distribution with Volume II being distributed only on request.